In general, secondary batteries refer to chargeable and dischargeable, unlike primary batteries that are not chargeable. The secondary batteries are being widely used in the high-tech electronic fields such as mobile phones, notebook computers, and camcorders.
Such a secondary battery comprises an electrode assembly and a case in which the electrode assembly is accommodated. The electrode assembly has a structure in which a plurality of electrodes and a plurality of separators are alternately stacked on each other.
Also, the secondary battery is subjected to a charging/discharging process. Here, an electrode may be expanded to cause a change in interface between the electrode and the separator, and thus, the electrode assembly may be swelled. Particularly, when the secondary battery is changed in thickness or increases in resistance, the lifespan of the secondary battery may be reduced.